Thread: Horse pwr.

Google says 1800 W is 2.41383976 hp.

However thats a power consumption rating and not the actual power of the saw motor.

Any idea on how to figure the actual saw power, rather than it's power consumption?

Originally Posted by masher

Any idea on how to figure the actual saw power, rather than it's power consumption?

That depends on the efficiency of the motor. As a rule of thumb, bank on a loss (due to friction in the bearings, arcing of the brushes etc) of between 10 to 20%. This should put you in the ball park

I just purchased a brand new oz made 1hp electric motor.
its 240v and 4.6 amps or 1104 watts which is closer to 40%

But its an induction motor and its so long ago since I did my training I've forgotten typical allowances for universal (brush type) motors.

Originally Posted by rgum

What does my Makita 9 and a 1/4 ( 18oo watts ???? ) equate to in
H power.?


Cheers

One HP equals 750 watts. Two HP equals 1500 watts. 2.4HP equalw 1800 watts

based on a typical 40% loss allowance for efficiency its somewhere about
1-1/2 actual hp at the blade.

Due to the torque curve of a petrol motor you would need about 4 hp petrol engine to give the same performance. If you used a diesel you could get away with 3hp.

Hi Rgum,

the efficiency of electric tool motors is somewhere between 50 and 75%. That means: your 1800 Watts Makita saw will have an output of around 1100 to 1300 Watts, meaning (with 755 Watts equalling 1HP) approx. 1.5 HP. 1200 Watts saws are around 1 HP, 750 Watts saws are 1/2 HP. Therefore i don't understand why in America a 2000 Watts router is called a 3HP router. They probably overload it to such an extent that for a few seconds 3 HP can indeed be squeezed out of it before it burns, for the power consumption for an output of 2200 Watts would be an input of something between 4000 to 5000 Watts (at low rpm, efficiency is even worse than 50%). Otherwise, this figure of "3HP" would just be a lie. No motor on earth yields 100% efficiency.

Regards,

Gerhard Schreurs
Netherlands

What Phil and masher have said is right. Converting watts to horsepower is a simple calculation.

The efficiency of motors is a different question entirely. While it is very relevant, I don't know of any power tools where they measure the power (whether watts or hp) in actual effective output.

Originally Posted by jisk

What Phil and masher have said is right. Converting watts to horsepower is a simple calculation.

The efficiency of motors is a different question entirely. While it is very relevant, I don't know of any power tools where they measure the power (whether watts or hp) in actual effective output.

Efficiency equals input over output. Working out the input is easy the output is harder, you have to work out all the losses and summate them. That is why most motors are rated on their input power.

BTW three phase induction motors over 1 HP now have to comply with the current MEPS regulations it is illegal to import and sell motors that don't comply, this new standard became law around April last year, supplyers are alowed to still sell earlier MEPS standard motors provided they were imported before the new regulations came into effect untill old stock runs out. Single phase induction motors are exempt.

An electric motor is more efficient than a petrol or desil engine and delivers more torque than an engine.


Regards

Phil

I think that it will be better if we refer only to the Wattage of any electrical tool.

1 Electric HP = 746W but, what usually is indicated as the tool Wattage is the Input Power or the consumption.

The subject of HP is very "open" and can be presented in many ways while the Americans are taking the lead....6HP Shop-Vac???!!!.....
http://www.shopvac.ca/vacs/list.asp?...selCapacity=10

simple calculation is;

6HP x 746W = 4,478W !!!
4,478W : 120V = 37.3A !!!

I almost bought the shop-vac just to change the motor on my table saw...

Yes, of course when you look at the spec. you see 11A motor...1320W...(my simple Electrolux has 1700W)

I don't think that many houses in USA has minimum...40A circuits...

Bosch USA, also learnt the "Patent" and the Bosch 4000 table saw (the tween brother of the European GTS-10) motor of 1,800W "Became"....4HP (should be 2.4HP)...

In EU, normally, the tools power is given by Watt...I did not see any HP's here and that's better...not too much "space" for deceiving...

Usually, the motor efficiency is between 50~60% and there is one company that gives you both the input and the output power, Metabo...please look here
http://www.metabo.co.uk/metabo/handg..._01885_00.html

niki

If power tool companies were to give the true wattage or out put of their tools then you would really see the differance between an ozito and a festool power tool.

Most cheap tools have a horrid efficiency so they increase the input watts to make it look good but in reality most would not pull the skin of a rice pudding.

Originally Posted by Phil Spencer

Efficiency equals input over output. Working out the input is easy the output is harder, you have to work out all the losses and summate them. That is why most motors are rated on their input power.

Sorry Phil but motor efficiency is output over input.

To work out the maximum power produced by a motor, you must know its maximum torque.

Hi Elkangorito

I can see that you are "in the business" so can you please explain how the HP that is stamped on the machine nameplate is measures...it's very difficult for me to believe that an 11A - 120V motor can develop 6 HP (it's a shop-vac motor)...that is better than most of the table saws motors on 120V one Phase

Regards
niki